Interpretive Summary:
Cotton is one of the most dominant and important field crops in the same southeastern states that also produce much of the US poultry. Cotton in this region is increasingly grown without tillage to help conserve soil and reduce cost. Whether poultry litter, which is generated in abundance in the southeastern US, is an effective fertilizer for cotton grown without tillage has not been adequately investigated particularly in highly erodable and marginal soils. This research was conducted to test the effectiveness of fertilizing no-till cotton with broiler litter in contrast to fertilization with conventional fertilizers in a Mississippi upland soil. The results showed broiler litter is a more effective cotton fertilizer than conventional commercial fertilizers in this soil type regardless of whether the cotton was grown on tilled or untilled soil. This effectiveness most likely is because litter is a rich source of nearly all mineral nutrients and is beneficial in other ways.
Broiler litter contains nutrients that can be lost by volatilization and in runoff water when the litter is applied on the surface and not mixed with the soil. Fertilizing no-till cotton with broiler litter implies it is applied on the surface and not soil incorporated. This in turn means some nutrients are lost to volatilization and runoff, a process that reduces litter fertilizer value. The second objective of this research was to quantify litter benefit reduction when litter is surface-applied and not soil incorporated. The results showed lack of incorporation in untilled soils reduces litter benefit but the reduction is small--about 8% cotton yield reduction. Lack of incorporation may not affect fertilizer value when the litter is applied to a freshly tilled soil under conventional-till systems.

Technical Abstract:
The effectiveness of poultry litter as cotton fertilizer is not well documented for upland soils in the southeastern USA where cotton may be grown under no-till and other soil conservation practices. The objective of this research was to measure the response of cotton to broiler litter fertilization in contrast to inorganic N fertilization and to quantify litter benefit reduction due to lack of incorporation under no-till and conventional-till systems in an upland soil. Six treatments were tested in two unreplicated adjacent fields, one under no-till (NT) and the other under conventional-till (CT) management, from 2003 to 2006 near Pontotoc, MS. The treatments consisted of an unfertilized control (UTC), a standard fertilization (STD) with urea-ammonium nitrate solution (UAN) to meet 100% of the N need (101 kg N/ha), fertilization with '5.2 Mg ha-1 incorporated or unincorporated broiler litter to supply 67% of the N need plus UAN to supply 33% of the N need, and fertilization with '7.8 Mg ha-1 incorporated or unincorporated broiler litter to supply 100% of the N need. Lint yield results showed broiler litter was a more effective cotton fertilizer than inorganic fertilizer under both NT and CT. The UTC produced an average across years of 870 kg ha-1 lint under NT and 1105 kg ha-1 under CT. The STD treatment increased yield over the UTC by only 121 kg ha-1 (14%) under the NT and did not affect yield under the CT. Fertilization with litter-alone when incorporated increased lint yield by 260 kg ha-1 (30%) under NT and by 137 kg ha-1 (12%) under CT. The yield of this incorporated litter-alone treatment exceeded the yield of the STD treatment by 139 kg ha-1 (14%) under NT and by 115 kg ha-1 (10%) under CT. Fertilization with litter also resulted in greater leaf area index but less chlorophyll index than the STD treatment, a response which suggests the better yield performance of litter fertilization is due to other nutrients and factors than N nutrition alone. Lack of litter incorporation reduced yield by up to 84 kg ha-1 under no-till but did not affect yield under conventional-till. Overall, broiler litter appears to be a more effective cotton fertilizer than conventional inorganic N fertilizers for this upland soil, but lack of incorporation under no-till may reduce this benefit.